1. Field of the Invention
The invention relates generally to methods and systems for analyzing data generated in oilfield exploration. More particularly, the invention relates to methods and systems that facilitate the analysis of downhole data or bottom-hole assembly data.
2. Background Art
Wells are generally drilled into the ground to recover natural deposits of oil and gas trapped in geological formations. A well is drilled into the ground and directed to the targeted geological location from a drilling rig at the Earth's surface. While the well is being drilled or after it is drilled, drillers often investigate the formation and its contents using various sensors, such as resistivity sensors, nuclear magnetic sensors, neutron sensors, gamma ray sensors, etc. These sensors may be lowered into the well on a wireline to take measurements after the well is drilled. Alternatively, the measurements or logging may be performed while drilling (MWD or LWD). With MWD or LWD, the sensors are included in a bottom hole assembly (BHA). A typical BHA includes the drill bit and a plurality of subassemblies (subs) that house various sensors. Data may be obtained about the borehole and drilling fluid properties in the borehole or about the properties of the formation and formation fluids. These data are generally referred to as downhole data.
Due to different properties of the sedimentation layers in the formation, formation stresses and formation fluid pressures may be different in different regions of the borehole, leading to washouts in some regions. These factors combined can produce a borehole that is irregular in shapes and sizes. These irregular shapes and sizes may cause the BHA to have irregular motions, such as different rotation speeds, wobbling, or vibration. The irregular motions of the BHA may have an adverse impact on the accuracy of the BHA or downhole data.
Therefore, it is desirable to be able to visualize (or recreate) the BHA and related data alongside a three-dimensional (3D) borehole trajectory so that the BHA data may be correlated with other data, e.g., logging data (3D images), caliper data (3D borehole shape), etc., alongside the 3D borehole trajectory. Particularly, it would be desirable to be able to correlate any anomaly in the BHA data with other data.
Visualization of a borehole trajectory presents unique problems. The thin and long 3D structure of the wellbore (typically having a diameter of 1 foot or less and a length of several miles) makes it difficult for a user to see the overall picture of the borehole and, at the same time, to see the detailed structures of the borehole. Published U.S. Patent Application No. 2003/0043170 A1 by Fleury and published U.S. Patent Application No. 2003/0234782 A1 by Terentyev et al. disclose methods that are particularly suitable for displaying the 3D borehole trajectory to facilitate data analysis. Co-pending U.S. patent application Ser. Nos. 10/604,062 and 10/250,049, both by Fleury et al., filed on Nov. 4, 2003, disclose methods for conveniently displaying multiple sets of formation measurement data alongside the 3D borehole trajectory.
There still exists a need for convenient methods and systems that permit the user to observe the BHA data in 3D and to correlate the BHA data or BHA motions with other data displayed along the 3D borehole trajectory.